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International Standard Bible Encyclopedia [1]

kus´tum (usage): In the Old Testament, except,   Genesis 31:35 where the Revised Version (British and American) renders, better, "manner" ( דּרך , derekh , "way"), the words translated "custom" are ḥōḳ , ḥuḳḳāh , "statute," and mishpāṭ , "judgment." Such passages as  Judges 11:39;  Jeremiah 32:11 , and especially  Ezra 3:4 (the King James Version "custom," the Revised Version (British and American) "ordinance"), illustrate the difficulty of deciding upon the proper translation, in cases where "custom" might become "statute," "usage" establish itself as "law." In   Leviticus 18:30;  Jeremiah 10:3 the reference is to heathen religious practices.

In the New Testament  Luke 1:9;  Luke 2:42;  Acts 6:14;  Acts 15:1 (the King James Version "manner");   Acts 16:21;  Acts 21:21;  Acts 26:3;  Acts 28:17 ( ἔθος , éthos ), and  Luke 2:27 from the same Greek root, refer likewise to definitely established religious practices; in every case except   Acts 16:21 , those of the Jewish law. The Revised Version (British and American) makes the translation of ethos uniform, reading "custom" in  Luke 22:39 (the King James Version "wont") and in   John 19:40;  Acts 25:16;  Hebrews 10:25 (the King James Version "manner"). Greek εἰωθός , eiōthós , from the same root, is rendered "custom" in  Luke 4:16 by English Versions of the Bible, and by the Revised Version (British and American) also in   Acts 17:2 , its only other occurrence in the New Testament. In  John 18:39;  1 Corinthians 11:16 "custom" is the translation of Greek sunḗtheia , in the sense of "usage" rather than of "law."